RESUMEN
Polyacrylic acid functionalized Fe3O4 nanoparticles (PAA-MNPs) of average size of 10 nm are prepared by a simple soft chemical approach. These PAA-MNPs are conjugated with folic acid through peptide bonding between the carboxylic group on the surface of PAA-MNPs and the amine group of folic acid. The good colloidal stability of FA conjugated MNPs makes it a promising candidate for targeted drug delivery, hyperthermia and as a MRI contrast agent with a transverse relaxivity R2 value of 105 mM(-1) s(-1). Folic acid conjugated magnetic nanoparticles (FA-MNPs) achieved â¼ 95% loading efficiency of doxorubicin (DOX) which could be due to strong electrostatic interaction of highly negatively charged FA-MNPs and the positively charged DOX. The drug release study shows a pH-dependent behavior and is higher in acidic pH (4.3 and 5.6) as compared to the physiological pH (7.3). Flow cytometry and confocal microscopic image analysis reveal that around 75-80% of HeLa cells undergo apoptosis due to DNA disintegration upon incubation with DOX-MNPs for 24 h. DOX-MNPs exhibit the synergistic effect due to the combination of DOX induced apoptosis and magnetic hyperthermia treatment (MHT) which enhance the cell death â¼ 95.0%. Thus, this system may serve as a potential pH sensitive nanocarrier for synergistic chemo-thermal therapy as well as a possible MRI contrast agent.
Asunto(s)
Medios de Contraste/química , Ácido Fólico/química , Nanopartículas de Magnetita/química , Antibióticos Antineoplásicos/química , Antibióticos Antineoplásicos/toxicidad , Apoptosis/efectos de los fármacos , Medios de Contraste/síntesis química , Doxorrubicina/química , Doxorrubicina/toxicidad , Portadores de Fármacos/química , Células HeLa , Humanos , Concentración de Iones de Hidrógeno , Hipertermia Inducida , Imagen por Resonancia Magnética , Nanopartículas de Magnetita/ultraestructura , Microscopía Confocal , Neoplasias/diagnóstico por imagen , Radiografía , Espectroscopía Infrarroja por Transformada de Fourier , TemperaturaRESUMEN
PURPOSE: To evaluate the shear bond strength (SBS) between zirconia and veneering ceramic following different surface treatments of zirconia. The efficacy of an experimental zirconia coating to improve the bond strength was also evaluated. MATERIALS AND METHODS: Zirconia strips were fabricated and were divided into four groups as per their surface treatment: polished (control), airborne-particle abrasion, laser irradiation, and application of the experimental coating. The surface roughness and the residual monoclinic content were evaluated before and after the respective surface treatments. A scanning electron microscope (SEM) analysis of the experimental surfaces was performed. All specimens were subjected to shear force in a universal testing machine. The SBS values were analyzed with one-way ANOVA followed by Bonferroni post hoc for groupwise comparisons. The fractured specimens were examined to observe the failure mode. RESULTS: The SBS (29.17 MPa) and roughness values (0.80) of the experimental coating group were the highest among the groups. The residual monoclinic content was minimal (0.32) when compared to the remaining test groups. SEM analysis revealed a homogenous surface well adhered to an undamaged zirconia base. The other test groups showed destruction of the zirconia surface. The analysis of failure following bond strength testing showed entirely cohesive failures in the veneering ceramic in all study groups. CONCLUSION: The experimental zirconia surface coating is a simple technique to increase the microroughness of the zirconia surface, and thereby improve the SBS to the veneering ceramic. It results in the least monoclinic content and produces no structural damage to the zirconia substructure.